1. Field of the Invention
This invention relates to a display device, and more particularly to a display device such as an organic EL (electroluminescence) element where a display portion is formed on a substrate.
2. Description of the Related Art
As disclosed, for instance, in Japanese Patent No. 2911552 and Japanese Unexamined Patent Publication No. 2002-18994, there has been known an organic EL element comprising an insulating transparent substrate, a plurality of transparent anodes on the substrate spaced from each other, an organic compound layer which includes at least a light emitting layer and is formed to cover the transparent anodes, and metal cathodes opposed to the transparent anodes intervening therebetween the organic compound layer.
In the organic EL element, the light emitting layer included in the organic compound layer emits light when an electric current flows between the transparent anodes and the metal cathodes, and the light is taken out through the transparent anodes and the transparent substrate. That is, in the organic EL element, each intersection of the transparent anodes and the metal cathodes forms a light emitting portion and light emitting portions can be controlled to emit light (light-emission) and not to emit light (non-light-emission) independently of each other. The organic EL element is excellent in wavelength stability.
In the display device where a display portion is formed on a substrate like an organic EL element, especially, when a resin substrate formed of macromolecular material is used as the substrate, there has been a problem that oxygen or water passing through the substrate can penetrate to the display portion to deteriorate the display portion. In order to deal with the problem, it has been proposed to provide a gas barrier layer between at least a part of the substrate and a display portion as disclosed, for instance, in Japanese Patent No. 2911552 and/or Japanese Unexamined Patent Publication No. 2002-18994. The gas barrier layer is a layer which basically blocks gases but naturally blocks liquids.
Especially in the display device disclosed in Japanese Unexamined Patent Publication No. 2002-18994, it is proposed to provide the gas barrier layer on each of the principal sides of the substrate, thereby reducing the gas-transmittivity of the substrate by increasing the density of the substrate by the compression due to the gas barrier layers.
Further, in the display device disclosed in U.S. Pat. No. 6,653,780, it is proposed to prevent deformation of the resin substrate due to stress of metal electrodes by forming metal film on the resin substrate, which forms auxiliary electrodes, so that the total stress on the metal film does not exceed a predetermined value.
In the display device having a gas barrier layer disclosed in Japanese Unexamined Patent Publication No. 2002-18994, tensile stress is constantly imparted to the gas barrier layer and when the overall device is bent, bending stress is also imparted to the gas barrier layer, which gives to a problem that the gas barrier layer is apt to be damaged.
Further, in the display device having a gas barrier layer disclosed in U.S. Pat. No. 6,653,780, though deformation of the resin substrate due to the stress of the metal electrodes is taken into account, stress when the overall device is bent is not taken into account. Accordingly, a problem that the gas barrier layer is apt to be damaged when the overall device is bent arises.